Schiff Bases and Their La(III) Complexes: Conventional and Microwave-Assisted Synthesis, Physicochemical and Spectroscopic Analysis
Two lanthanum(III) Schiff base complexes, 2,2'-((1E,1'E)-((2,2-dimethylpropane-1,3-diyl)bis (azanylylidene))bis(methanylylidene))diphenollanthanum(III) [La(AD1H)] and 6,6'-((1E, 1'E)-((2,2-dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))bis(2- methoxyphenol) lanthanum(III) [La(AD1OMe)] were successfully synthesized. The complexes were prepared by conventional reflux and microwave-assisted synthesis methods where a minimum amount of solvent was used, with a shorter reaction time for the latter. Both ligands and their lanthanum(III) complexes were characterized by spectroscopic and physicochemical analyses. The shift of ν(C=N) to a higher frequency by 15-18 cm-1 indicated that the complexation to La(III) through the azomethine N was established. It was further supported through the shifting of the azomethine proton signal to higher chemical shifts with ∆δ=0.19-0.23 ppm. In addition, the shifting of the n‒π*(C=N) band in UV-Vis spectra with ∆λ= 2‒16 nm also indicated the involvement of azomethine nitrogen in the complexation.